Comparison of Epidemiology and Clinical Outcomes of Influenza A & B Cases in Manitoba, Canada

• Age-adjusted incidence rates of hospitalization and death occurring within 1 month of the diagnosis of influenza [ Time Frame: up to 21 years ] [ Designated as safety issue: No ]
  Data records of hospitalization and death occurring within 1 month of the diagnosis of influenza, overall and stratified by demographic and clinical characteristics
  
  

• Annual incidence rates of influenza A and B cases [ Time Frame: up to 21 years ] [ Designated as safety issue: No ]
  Age adjusted incidence rates of influenza A and B cases among the whole Manitoba population.
  
  
• Annual incidence rates of influenza A and B cases among certain subsets of the population [ Time Frame: up to 21 years ] [ Designated as safety issue: No ]
  Age-adjusted (when appropriate) annual incidence rates of influenza A and B cases among certain subsets of the Manitoba population.
  
  
• Visits to health care provider within 6 months of the diagnosis of influenza [ Time Frame: up to 21 years ] [ Designated as safety issue: No ]
  Age-adjusted rate of visits to health care providers within 6 months of the diagnosis of influenza, overall and stratified by demographic and clinical characteristics.
  
  

Annual epidemics of influenza are an important public health problem globally and in Canada. Each year, 10-25% of the Canadian population become infected with influenza. Most of these infections are typically asymptomatic or associated with a mild self-limiting illness. However, influenza can cause severe illness leading to hospitalization and death, especially among the very young, the elderly and among those with underlying chronic conditions. It has been estimated that on average about 4,000 influenza-related deaths occur in Canada each year. In addition, the economic burden of influenza is significant because of the high direct costs associated with increased utilization of services and the indirect costs caused by school and work absenteeism.

This project compares laboratory-confirmed cases of influenza A and B in terms of their epidemiology and clinical outcomes, and describes the comparative epidemiology of laboratory-confirmed influenza A and B cases in Manitoba over the period from 1990 to 2011.

This analysis compares, by influenza type, the overall and cause-specific incidence rates of physician encounters, hospitalization and death following the diagnosis of a laboratory-confirmed influenza. It also describes multivariate models to assess the effects of influenza type on clinical outcomes (e.g., hospitalization) while accounting for confounding by demographic, socioeconomic, geographic and clinical (e.g., co-morbidity, immune status) characteristics.

The study also assesses secular and seasonal trends in the incidence rates of influenza A and B cases in Manitoba during the period of 1990-2011, excluding the 2009 H1N1 pandemic period (April 2009-April 2010) and assesses whether these rates vary for different subsets of the population defined by demographic (e.g., age group, gender), socioeconomic, geographic (neighborhood of residence) and clinical (e.g., vaccination, presence of chronic conditions, immune status) characteristics.